In recent years, research and development efforts have been paid on liquid lenses as a form of lens having variable refracting power. Liquid lenses can be classified into several types and a type of liquid lens whose refracting power can be changed by changing the curvature of the flexible member that is arranged adjacent to liquid in the liquid lens is known. At present, liquid lenses of this type are expected to be applicable to various optical systems because they are highly responsive and resistant against disturbances such as vibrations. PTL 1 discloses a technique of reducing the density difference between the two different liquids arranged adjacent to a flexible member for the purpose of making the refractive surface of the flexible member close to a spherical surface.